1. Field of the Invention
The invention relates in general to a pre-driver, and more particularly to a pre-driver having a stable output common mode voltage and a stable output swing.
2. Description of the Related Art
Conventionally, a pre-driver has been applied to the high speed digital data transmission technology, and has been widely applied to various occasions, including, for example, a SerDes. Generally, the pre-driver provides a stable input common mode voltage level, which enabling the high speed transmitter operating in conjunction with the pre-driver to have better output signal quality.
In the prior art, however, the pre-driver often encounters a trade-off situation, in which the operation speed and the slew rate cannot be simultaneously satisfied due to an excessively-large swing of the output signal. In addition, the slew rates are different during the rising and falling periods of the output signal. Moreover, the pre-driver have other problems such as an unstable common mode voltage level and high sensitivity to power noise. As a result, the signal quality of the high speed transmitter is adversely affected.
Thus, it is an important direction in the industry to design a pre-driver capable of effectively providing coordinated parameters, such as output signal swings, operation speed and slew rate while having a better control of common mode voltage and slew rate.